DESCRIPTION (based on application?s abstract): In health services research, it is assumed that there are optimal health care delivery factors that result in superior clinical outcomes. "Center effects" are differences in outcome among centers that cannot be explained by identifiable differences in patients? diseases, or treatments applied, and are presumed to result from differences in the way health care is delivered. Procedure volume is the central focus of many studies on center effects because it is readily available, while cataloguing details of health care delivery across centers in the United States is labor-intensive. It is not known whether procedure volume performed in a center directly affects outcomes or is a surrogate measure for other factors that are associated with improved outcomes and larger volumes. This study will comprehensively evaluate the association of treatment center characteristics and clinical outcomes in the setting of hematopoietic stem cell transplantation (HSCT) for malignant hematologic disorders using a retrospective cohort study design. The following treatment center characteristics will be collected: a) physician and health care provider characteristics; b) transplant unit resources; and, c) medical center organization. Association of these characteristics with treatment-related mortality and overall survival will be evaluated after adjusting for clinical prognostic factors. Models evaluating the impact of modifying treatment center features with clinical outcomes will be constructed. The study will be conducted at the Statistical Center of the International Bone Marrow Transplant Registry / Autologous Blood and Marrow Transplant Registry (IBMTR/ABMTR) in Milwaukee, utilizing available clinical data reported by 175 HSCT centers in the United States, representing 4,675 patients. Results of this study will provide information important for decision making by individual centers regarding program growth and development, and will inform policy makers, accreditation bodies, and third party payers in their attempts to regulate and improve quality of care for transplant recipients. This study should direct attention to health care parameters important for development of standards of medical care for autologous and allogeneic transplantation.